Calculators · Epoxy Calculator
InteriorEpoxy Calculator
Enter the area and pick a product or a thickness to get gallons of epoxy to buy. Coverage comes from manufacturer data sheets.
Epoxy needed
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How to calculate how much epoxy you need
There are two ways to size epoxy. A floor coating is bought by the coverage the manufacturer prints on the label. A pour or a thick build is sized by volume. The calculator does both with the same list of areas.
| Method | Formula |
|---|---|
| By product coverage | gallons = area (ft²) × coats ÷ coverage (ft² per gallon per coat) |
| By thickness | gallons = area (ft²) × 144 × thickness (in) ÷ 231 ÷ (solids ÷ 100) |
| Extra and rounding | multiply by (1 + extra ÷ 100) and round up to a whole gallon |
The thickness method is geometry. A US gallon is 231 cubic inches, a square foot is 144 square inches and a mil is a thousandth of an inch. One mil over one square foot is 0.144 cubic inches, so one gallon of a 100% solids epoxy covers about 1,604 square feet per mil of thickness. The solids by volume figure is the share of the wet product that stays as cured film, so the wet volume you need is the film volume divided by it. The calculator reads measurements typed like 10'6" or 10 ft 6 in, and for a round area you pick “Circle” and type the diameter.
Example: a 20 ft by 24 ft garage floor
A garage floor measures 20 ft by 24 ft. You choose the Griot’s Garage Industrial Epoxy Floor Coating, whose data sheet gives 200 to 350 square feet per gallon per coat and recommends a minimum of 2 coats.
| Step | Operation | Result |
|---|---|---|
| Floor area | 20 × 24 | 480 ft² |
| Gallons, lower coverage | 480 × 2 ÷ 200 | 4.8 gallons |
| Gallons to buy | 4.8 rounded up | 5 gallons |
| Gallons, upper coverage | 480 × 2 ÷ 350 | 2.74 gallons |
The result shows 4.80 gallons, 5 gallons to buy, and a range of 3 to 5 gallons for the whole 200 to 350 range. The calculator uses the lower coverage for the main figure so that you do not run short. Griot’s own sheet estimates 3 to 4 gallons for this garage. Its lower coverage figure gives 4.8. Kits come in set sizes, so check how many kits cover the gallons.
How many square feet does a gallon of epoxy cover?
The table copies the coverage from two manufacturer data sheets, checked in October 2026. Both are for floors and both vary with the application method. Choose “Custom coverage” if your product is not in the list.
| Product | Coverage per gallon | What the sheet says |
|---|---|---|
| ArmorPoxy ARM707X-RM, 100% solids | 115 to 170 ft² | Practical coverage at the recommended thickness of 8 to 12 mils. Mix ratio 2 parts A to 1 part B. Sold in 1.5, 3 and 15 gallon kits. |
| Griot’s Garage Industrial Epoxy Floor Coating, water-based | 200 to 350 ft² per coat | A minimum of 2 coats is recommended, which gives 100 to 175 ft² per gallon. Solids by volume 43.5%. Supplied as a complete A+B kit of 1.25 gallons. |
The ArmorPoxy practical range is lower than the theoretical 134 to 201 square feet per gallon that the thickness method gives for 12 and 8 mils. The sheet does not explain the difference, so use the practical figure when you buy by coverage.
Gallons of a 100% solids epoxy by thickness
Gallons for common areas at 8, 12 and 20 mils, with no allowance for waste. This is the thickness method with solids at 100.
| Area | 8 mils | 12 mils | 20 mils |
|---|---|---|---|
| 100 ft² | 0.50 | 0.75 | 1.25 |
| 200 ft² | 1.00 | 1.50 | 2.49 |
| 400 ft² | 1.99 | 2.99 | 4.99 |
| 500 ft² | 2.49 | 3.74 | 6.23 |
Tips for ordering
- Read the label for the coverage and the number of coats. Type the coverage into “Custom coverage” if your product is not listed.
- Add one area for each separate section, or use a circle for a round one.
- Use the extra box for the allowance your installer or the manufacturer recommends. It is added before the gallons are rounded up.
- Use the thickness option for pours such as tables and bar tops. For a 100% solids epoxy keep the solids at 100.
- To size the floor first, use the square footage calculator. For paint on walls, use the paint calculator.
Frequently asked questions
How do I calculate how much epoxy I need?
Measure the area in square feet, then divide by the coverage of one gallon per coat, and multiply by the number of coats. A 20 ft by 24 ft garage is 480 square feet. With a coating that covers 200 square feet per gallon per coat and two coats, that is 480 × 2 ÷ 200 = 4.8 gallons, so 5 gallons. If you know the thickness you want instead, use the thickness option. It works from the fact that one US gallon is 231 cubic inches.
How many square feet will 1 gallon of epoxy cover?
It depends on the product and the thickness. The data sheets we checked in October 2026 give 115 to 170 square feet per gallon for a 100% solids epoxy at 8 to 12 mils, and 200 to 350 square feet per gallon per coat for a water-based epoxy. For a 100% solids product, one gallon spreads over about 1,604 square feet divided by the thickness in mils.
How much epoxy do I need for 100 square feet?
With the two products we checked, about 0.6 to 1 gallon. The 100% solids epoxy needs 0.59 to 0.87 gallons for one coat, and the water-based epoxy needs 0.57 to 1.0 gallons for two coats. A 100% solids epoxy poured at 12 mils needs 0.75 gallons. Pick your product in the calculator for your own figure.
How much epoxy do I need for a 10 by 10 room?
A 10 ft by 10 ft room is 100 square feet, so the answer is the same as for 100 square feet. Type 10 and 10 in the calculator, choose your product or your thickness and read the gallons. Add an extra percentage if the manufacturer or your installer recommends one for your surface.
How do I calculate epoxy for a pour or a table?
Choose “By thickness”, type the length and width and the depth of the pour. The calculator multiplies the volume in cubic inches and divides by 231 to get gallons. In fluid ounces, divide the cubic inches by 1.805. For a 100% solids epoxy leave the solids at 100.
Does the coverage change from job to job?
It can. The manufacturers quote ranges. The ArmorPoxy sheet says coverage will vary with the application method, and the Griot’s sheet says results can differ with mixing, equipment, temperature, application method and site conditions. The calculator uses the lower figure of the range, which gives more epoxy, and shows the result for the upper figure too.
How much does epoxy cost per gallon?
Prices change by brand, region and kit size, so this calculator does not show them. Take the gallons from the result and ask local suppliers for a quote in the same unit.
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